This invention relates to electric arc welding and more particularly to an arc welding torch having an improved integral optical system which provides real time images of the weld region.
Good arc welds are achieved by controlling weld current, weld penetration, centering of weld puddle over part seam, seam bead lay rates, etc. Open loop machine welding, in which weld parameters are selected on the basis of past experience, does not produce good welds. For consistently good machine welding, sensing of the weld area and weld puddle characteristics and using this information as feedback to control the welding process is needed. Some experiments have been conducted at the Ohio State University Center for Welding Research in which the weld puddle has been viewed by an overhead optical system looking down over the welding electrode. In these experiments, the conventional welding torch, open optical system, and video camera were carried on a large platform unsuitable for any practical welding application. Refer to CWR Technical Report 529613-81-3, S. H. Rao, September 1981, especially pages 27-33.
In concurrently filed application Ser. No. 401,471, A. W. Case, Jr., N. R. Kuchar, and D. C. Peroutky, "Arc Welding Torch with Integral Vision Sensor", assigned to the same assignee, the optical torch has a configuration that makes it suitable for industrial welding. The center of the torch is cleared and presents minimum obstruction to passage of light to the optical lens; the slim profile electrode holder is out of focus and not evident in the image of the weld puddle and weld area. When coupled to a remote video-like camera and controller, the torch-vision system permits control of torch manipulation and of the weld process. One embodiment of this torch is shown in FIGS. 1, 2, and 5 and is described in detail.
Due to the incomplete blocking of light from the arc by the tungsten electrode, an over-saturated image occurs near the electrode. This is because the brightness of the electric arc is many times the brightness of the surrounding area illuminated by the arc. Since it is desired to image the area surrounding the arc, the presence of the arc overloads the sensor locally.